1. Field of the Invention
The present invention relates to a substance of superconductive conjugate photoconductivity in parallel to superconductivity in a composition range outside the superconductive composition region within the Bi-SrCa(LaY)-Cu-O oxide system and a method for producing the same and a superconductive optoelectronic device with the same.
Here, I define "Superconductive-Conjugate Photoconductivity" to be a substantially new type of large photoconductivity in basic substances or host insulators which emerges in several steps with decreasing temperature in accordance or correspondence with the critical temperatures of superconductivity in relevant conductive substances, all based on the discoveries and inventions disclosed by the present inventor in that "Photoconductivity" and "Superconductivity" are conjugate with each other in a certain group of oxide superconductors.
2. Related Art Statement
The present inventor has presented series of substances having photoconductivity as the substances close to but outside of superconductive region in the prior art, and has already filed patent applications related to substances in the Y.sub.3-x Ba.sub.x -Cu.sub.y -O.sub.z oxide system of superconductive photoconductivity (Japanese Patent Application Laid-open No. Hei-1(1989)-201058), to substance in the La.sub.2 -Cu.sub.1 -O.sub.z system of superconductive photoconductivity (Japanese Patent Application Laid-open No. Hei-1(1989)-201059), to substance in the Ba.sub.1 -Pb.sub.1-x -Bi.sub.x -O.sub.z oxide system of superconductive photoconductivity and a method for producing the same (Japanese Patent Application Laid-open No. Hei-2(1990)-51423) and to substance in the Ca.sub.(X-x) -Sr.sub.x -Bi.sub.(Y-y) -Cu.sub.y -O.sub.z oxide system of superconductive photoconductivity and a method for producing the same (Japanese Patent Application Laid-open No. Hei-2(1990)-51424).
Before 1986, superconductive materials have signified essentially metals and alloys thereof. However, recent oxide high temperature superconductors (such as the Y-Ba-Cu-O oxide superconductor) are originally insulators or semiconductor and have been doped by using a large amount of additional elements (such as Ba, Sr) for the purpose of increasing hole density and improving the critical temperature. Therefore, experiments of optical properties in the vicinity of their optically visible range were mainly limited to measurements of optical reflection or scattering by reflecting metallic properties thereof.
An incident light reflects or scatters on the surface of superconductor, but never enters into a superconductor, so that superconductivity and optical properties such as absorption have been usually considered to be irrelevant, except reflection and scattering of light, in domestic scientific societies and international conference abroad.
The reason thereof is because superconductivity are considered to be incompatible physical properties with absorption and photoconductivity and the stability of a superconductor is broken by irradiating light in the wavelength range of shorter than those relevant to the gap energy of the BCS theory. However, there exist reasonably clear correlations between photoconductivity in insulator and superconductivity in the oxide materials such as the Y-Ba-Cu-O, La-Cu-O, Ba-Pb-Bi-O systems of oxide material and the like. Therefore, if a substance having either one or both of deeply correlated superconductivity and photoconductivity is obtained, it becomes possible to utilize it to compose devices such as an optically controllable Josephson element or a superconductive phototransistor and the like and eventually to manufacture apparatus having both properties of machinery and tools of "superconductive computer" based on the presently pursued Josephson element and of "optical computer" proposed by optoelectronics, that is, "superconductive optical computer" and the like.